In recent years, an optical communication system (digital optical communication system) based on a digital signal processing technique such as a digital coherent transmission technique is put into practical use. In a digital optical communication system as described above, linear waveform distortion occurring from an influence of wavelength dispersion of an optical fiber being a transmission path is compensated by performing waveform equalization processing with use of a digital signal processing circuit in an optical transmitter/receiver (line card) of an optical transmission apparatus. By performing waveform equalization processing with use of a digital signal processing circuit as described above, it becomes possible to perform high-accuracy waveform distortion compensation, and it becomes possible to implement an optical communication system having programmability compatible for transmission paths of various types.
PTL 1 describes a digital optical communication system including a compensation unit (DCM: Dispersion Compensation Module) for compensating a part of wavelength dispersion which is occurring in an optical signal transmitted by a transmission path, a reception unit for receiving an optical signal after compensation by the compensation unit, a conversion unit for converting an optical signal received by the reception unit into an electric digital signal, and a digital processing unit (DSP: Digital Signal Processor) for compensating, by digital signal processing, wavelength dispersion remaining in the digital signal.